function y=Xp(x)
    %y=exp(-4.2222)*0.7307*x^(0.7307-1);
    y=exp(-4.443)*0.7643*x^(0.7643-1);
    %y=exp(-2.12)*0.4562*x^(0.4562-1);
    %y=exp(-4.2222)*0.7307*x^(0.7307-1);
    %y=exp(-4.4435)*0.7643*x^(0.7643-1);
    %y=0.00728;
end